Sometimes wind can feel like a bit of a mystery because we can feel it, but not see it.
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Have you ever heard the wind whistle through the trees on a stormy night or had a light breeze cool you down on a hot, summer day? Sometimes wind can feel like a bit of a mystery because we can feel it, but not see it.
Wind is air in motion, both near the earth’s surface and high up in our atmosphere. Air is made of molecules, such as nitrogen and oxygen, and when these molecules move together in a direction, we get wind. Wind can vary in strength from a gentle breeze pushing a leaf along a path to a strong gale that can cause severe damage. The most powerful wind happens during storms like tornadoes and tropical cyclones.
The short answer is: a difference in temperature that creates a difference in pressure. Are you ready for a longer answer?
OK, here we go… Wind is caused by pressure gradient, or the difference between high and low pressure. Think about high pressure like the top of a hill and low pressure as the bottom of the hill. If you roll a ball from the top it will quickly rush down to the bottom. The same thing is happening with wind. Pressure gradient is the slope of the atmosphere and wind flows from high pressure (the top of the hill) to low pressure (the bottom of the hill). The larger the pressure gradient is, the stronger the wind will be.
This video might help you to understand pressure gradient:
When you talk about wind direction it is described by where the wind is coming from. So if the wind is blowing from the west to east, we call it westerly winds. Wind speed is often measured in kilometres per hour (km/h) or metres per second (m/s) and scientists often use a tool called an anemometer to measure the speed.
You may have heard meteorologists on TV talk about wind gusts, but this is not the same as wind speed. The difference is that wind speed is an average that is measured over a longer period of time while wind gust is a sudden increase in the wind’s speed that lasts no more than a few seconds.
Where do you think the strongest wind gust has been recorded in the world? It’s actually not too far from here. On 10 April, 1996, our neighbours on Barrow Island in western Australia recorded a 407 km/h wind gust during Tropical Cyclone Olivia! Can you think of something that moves that fast?
Did you know that the windiest city on earth is here in our very own Aotearoa? Can you guess where it is…?
Wellington! The annual average wind speed in our capital is a whopping 29 km/h!
Where is the wind coming from? Let’s make a wind vane to find out!
(The quiz works best on kahoot, but if you prefer a text version, you can download it as a PDF here).